Effects of temperature and salinity on germling development and fitness in the brown macroalga Fucus serratus L.

Document Type: Primary Research paper



Fucoid brown algae form extensive populations that dominate the intertidal and subtidal vegetation on temperate rocky shores. The persistence of populations of fucoid brown algae depends on their reproductive ability and the survival and growth of early life history stages (germlings) that are generally more susceptible to stressors than adults. In this study, the effects of temperature and salinity on germling development and fitness in the brown macroalgae Fucus serratus is assessed by studying rhizoid elongation, photosynthetic performance and survival in a matrix of four different temperatures and three salinities. It was hypothesized that both lower and higher than normal temperatures (12°C - 17°C) would constitute environmental stress and affect germling fitness, and that these effects would be exacerbated by sub-oceanic salinities below 32 psu. The results show that temperatures lower than the normal summer temperatures (6°C) have significant negative effects on both growth and survival as well as on photosynthesis, while there are no effects of higher than normal temperatures (22°C) alone. Sub-oceanic salinities affect growth and survival negatively, but only at the lowest salinity (18 psu), and have no effect on photosynthetic parameters. We conclude that higher water temperatures will not affect germling fitness, and thus F. serratus persistence, negatively, but low salinities and lower water temperatures will.